New security requirements go into effect Friday at airports throughout the United States. All checked baggage has to be screened before being loaded aboard a plane. Airline officials say they are hopeful the new security measures will not mean delays for passengers.

At the world's busiest airport, Chicago's O'Hare, city Aviation Commissioner Tom Walker told reporters Thursday that airlines serving both city airports are ready to comply with the new regulations.

"There are various methods authorized by the law to provide that screening. The airlines will be incorporating some or all of the accepted methods in their daily operations," he said.

Beginning Friday, all checked baggage has to be screened, either with an explosive detecting machine, a bomb-sniffing dog, a hand search of the bag, or bag matching making sure no bag gets on a plane unless its owner is also aboard. In Washington this week, transportation secretary Norman Mineta said the regulations will make flying safer.

"The system will be robust and redundant. We will be relentless in our search for improvements. It is better today than yesterday. It will be better still tomorrow," he said.

Critics of the regulations have pointed out that the United States has only 160 explosive-detecting machines for baggage nationwide, that hand-searching bags is time-consuming and that bag matching does little to guard against a suicide terrorist.

In Chicago, the major airlines say they are confident they can quickly screen passengers' bags and get them aboard the right planes without delaying flights. American Airlines spokeswoman Mary Francis Fagan says passengers are already coming to the airport two hours before their flights, and that should be enough time to inspect their luggage.

"Many of the carriers, American included, have already been implementing the changes that they must make for at least a week, in some cases longer," he said. "No one has seen indications that this will cause any consternation effective January 18."

Currently, less than ten percent of all the passenger bags carried aboard commercial airliners in the United States are screened. Todd Kealy was in line for a flight to Canada Thursday, and welcomes the tougher security measures.

"I think it is about time. I think the expectation of many passengers is that that was already happening," he said. "It is probably a little bit of a relief that it actually will happen."

This December, baggage security will be tightened yet again when the government requires all bags to be passed through explosive-detecting machines. FAA officials say that will mean buying about 1,800 more of the large, expensive machines for the nation's airports.